1. Field of the Invention
The present invention relates to a system for leveling vehicles, such as recreational vehicles relative to gravity and more particularly to systems for automatically leveling such vehicles. The invention is particularly adapted to be used in vehicles which employ hydraulic jacks to level the vehicles relative to gravity, but the invention may also be used with an air leveling system forming a part of the suspension of the vehicle.
2. Description of the Prior Art
Recreational vehicles are now in wide-spread use to provide families and individuals with vacation opportunities at relatively low costs. The recreational vehicles allows families and individuals to visit out of the way locations and to enjoy these locations at relatively low cost. The vehicles also provide such families and individuals with the opportunities to hunt, fish, hike and engage in a number of outdoor sports while being assured of adequate accommodations at these outdoor locations.
Quite often the recreational vehicles have to be parked at sites which are not level relative to gravity. This results from the fact that the campsite may be located in rugged terrain. However, to obtain the benefits from such camp sites, the recreational vehicle should preferably be level relative to gravity. For example, when the vehicle is level relative to gravity, dishes on dinning tables are stable and sleeping accommodations are superior since they are level and thereby more comfortable.
Since recreational vehicles are often parked at nonlevel sites, jacks have been provided to adjust the disposition of the vehicle so as the make the vehicle level relative to gravity. These jacks may be either hydraulically or electrically operated. The jacks are generally disposed at the corners of the recreational vehicle and are attached to the vehicle at the underside of the vehicle. The jacks may be individually operated to adjust the level of the vehicle relative to gravity. As it will be appreciated, the individual operation of the jacks is time consuming and additionally, it is difficult to be precise in the leveling procedure. It can be seen that such a difficult and time consuming procedure can be disturbing when an individual or family arrives tired and hungry at a campsite in the evening and then has to level the vehicle relative to gravity before the evening meal can be prepared and served and before the individual or family can then relax for the evening.
Since the recreational vehicle industry is relatively large, a considerable effort has been made and substantial sums of money has been extended to overcome the problems discussed in the previous paragraph. Some progress has been made. For example, the jacks in use have been improved through the years so that their performance is more reliable than the performance of the jacks manufactured and sold a number of years ago. In spite of such progress, however, problems still remain. Specifically, with jacks that have to be individually operated, there is no assurance that leveling of the vehicle relative to gravity can be accomplished in a reasonable period of time.
There have also been prior art systems for automatically leveling a vehicle relative to gravity. One prior art system, such as shown in my prior U.S. Pat. No. 4,597,584, includes a plurality of extendable jacks, preferably hydraulic, located at strategic positions at the bottom of the vehicle. A lurality of switches sense the downward tilting of the vehicle relative to gravity at the individual strategic positions and produce individual signals to individually operate the jacks in accordance with such tilting. The jacks are individually extended in a particular sequence depending upon the particular direction in which the vehicle is tilted relative to gravity.
In my prior art system, the jacks become extended when the hydraulic pressure in hydraulic circuit exceeds a particular value. The jacks tilted the greatest relative to gravity are initially extended. Since the rear of the vehicle weighs considerably more than the front, the switches are constructed and/or connected in a circuit to resolve any ambiguities in favor of initially operating the jack at the rear of the vehicle. A delay is preferably provided between the operation of each jack and the operation of the next jack in the sequence so that transients in the movement of the vehicle from the operation of each jack can be eliminated before the next jack is operated.
In addition, in my prior art system, when the vehicle has been leveled relative to gravity, any jacks still not engaging the ground are extended until they engage the ground with reduced force. In addition, in my prior art system, when the hydraulic forces in the jacks are less than a particular value and the vehicle is traveling between destinations, the hydraulic fluid in the jacks is slowly bled to a reservoir so that hydraulic forces cannot accumulate in the jacks to operate the jacks.
Although my prior system operated satisfactorily to automatically level the vehicle, there are still situations where there could be problems with the prior system. For example, in the prior automatic leveling system, one jack at a time was extended to level the vehicle. This could in some situations produce considerable stress and deflection in the vehicle. Also, there could be situations where a vehicle can be supported primarily from opposite corners, which again could provide considerable stress and deflection in the vehicle. It would, therefore, be preferable that as much as possible, the vehicle at all times should be supported at four places to thereby minimize any stress and deflection in the vehicle.